You want to know which default SMTP banners are added to the header of messages by Messaging Gateway for Service Providers when a message passes through it.
Messaging Gateway for Service Providers may add X-Brightmail-Tracker and X-BLTSYMAVREINSERT entries to the header when a message passes through it.
The X-Brightmail-Tracker entry is not added by default with all MTA integrations. Please see the Implementation Guide for details about enabling the tracker or SDK guide to integrate this option with the MTA. You can download manuals from the Documentation page.
The X-BLTSYMAVREINSERT header is added only when Messaging Gateway for Service Providers diverts the messages that contain known viruses through a virus cleaner and then re-inserts them into the mail stream.
SMTP banner entries added to the email header are primarily added by the MTA.